Is this story possibly true?

[Captain Kilowatt]

Are you ready?

Once upon a time I happened to be in a 'tour' group through a hydroelectric generating plant. Part of that tour was walking past one of the generators. That thing was about the size of a very 'pregnant' 15 - 20 foot 'Airstream' trailer. We were warned about wearing metal, having metal dental fillings, sutures, etc. We were told that at any sign of discomfort to not approach any closer to that generator. The areas around that generator were marked in various ways according to the severity of exposure too. There was absolutely no doubt when you got 'close enough'. I have no idea of the amount of current being produced by that generator, but would feel safe in saying it was more than you'd be exposed to near a 50Kw CB radio/amplifier. Those warning areas were in '10's of feet, not '100's of feet, and none of us were allowed to 'cheat' on how close we got, even if we had wanted to. I had dental fillings. I didn't want to do any of that 'cheating'. Ever have a filling and drink very cold water and regret it? I think you can get an idea from that.
If there was someone who was burned from RF exposure at 100 feet from that transmitter/antenna, and there -weren't- others closer screaming, I'd have to tend to believe that 'all' of the story isn't being told.
- 'Doc

I tend to agree Doc. That generator would have had a tremendous electromagnetic field and likely would have been producing several megawatts.

 

[mackmobile43]

4040 burned up all his joints and internal eye goo with his 3000a7 davemade input into an inferior antenna system which reflected a ton of watts and through the microphone through his body and eventually out his ass found a path to ground.

 

[Shockwave]

No doubt the FM station wants the height for coverage. Perhaps a better way to explain it would be a ground mounted 1/4 wave at 100 MHz or even 27 MHz is going to produce much higher levels of RF at ground level then a 1/4 wave at 1 MHz on the ground. When the entire antenna is inline with the body, you get a bigger dose of RF.

The dangers around a large generator are mostly magnetic. RF radiation at 60 cycles is considered very low especially before it goes through the step up distribution transformers. 50 KW of RF approaching the VHF spectrum is way different then anything running at 60 cycles. If there is something going on here beyond an intense magnetic field please tell me more?

I also don't think at 100 feet away this person received a serious RF burn from a short bracelet. I'm just saying I would not be quick to assume it's impossible. I guarantee if you hold an 8 foot whip 100 feet away your hand will start smoking! There is a chance 50 KW into a multiple element gain antenna firing directly at someone with a large metal bracelet could create heat one could feel on their wrist.

 

[W5LZ]

Shockwave,
I would have to agree, there is a chance that it could have happened. I also have to think that there being only one instance of something like that happening in those circumstances is very unlikely. Wouldn't you?
- 'Doc

 

[CTStallion]

Completely possible BUT......

If the transmitter was on 27 MHz AM side, it's more likely that the RF burn was due to a harmonic much higher in freq to which the wrist band was harmonically related & not the fundamental frequency.

 

[Shockwave]

For a bracelet to become resonate the frequency would have to be in the UHF spectrum. There is little chance any significant energy at these frequencies made it past the PI output network in that tube amp. Which of course makes getting the RF burn even less likely. W5LZ is also correct, this would be the first time in 30 years I've ever heard anyone getting an RF burn 100 feet away from a CB antenna.

 

[CTStallion]

For a bracelet to become resonate the frequency would have to be in the UHF spectrum. There is little chance any significant energy at these frequencies made it past the PI output network in that tube amp. Which of course makes getting the RF burn even less likely. W5LZ is also correct, this would be the first time in 30 years I've ever heard anyone getting an RF burn 100 feet away from a CB antenna.

It's not necessarily the RF (per se) at the fundamental or a harmonic frequency that would cause the 'burn', rather the: MAGNETIC FIELD created by the RF.

See attached for example:

IMRSER Page

They specifically warn against bracelets, jewelry, etc....

Could've been RF induced HEATING of the bracelet; the scientific term is called: RADIO INDUCED HYPERTHERMIA, and is quite 'common' at 13 & 27 MHz (in the HF spectrum), and ALL OVER the VHF/UHF/EHF/SHF <Microwave> range(s).

 

[Shockwave]

It's not necessarily the RF (per se) at the fundamental or a harmonic frequency that would cause the 'burn', rather the: MAGNETIC FIELD created by the RF.

See attached for example:

IMRSER Page

They specifically warn against bracelets, jewelry, etc....

Could've been RF induced HEATING of the bracelet; the scientific term is called: RADIO INDUCED HYPERTHERMIA, and is quite 'common' at 13 & 27 MHz (in the HF spectrum), and ALL OVER the VHF/UHF/EHF/SHF <Microwave> range(s).

CTStallion, Thank you for posting the article concerning MRI technology. I learned some things and got somewhat confused at the same time. How is it that a high power transmitting antenna produces no noticeable attraction to ferrous metals and yet the application of RF in the MRI machine can create a magnetic field strong enough to suck in metal from 10 feet away? Is there some way they are canceling the effects of the RF radiation and maximizing the electromagnetic effects?

 

[CTStallion]

CTStallion, Thank you for posting the article concerning MRI technology. I learned some things and got somewhat confused at the same time. How is it that a high power transmitting antenna produces no noticeable attraction to ferrous metals and yet the application of RF in the MRI machine can create a magnetic field strong enough to suck in metal from 10 feet away? Is there some way they are canceling the effects of the RF radiation and maximizing the electromagnetic effects?

Gud question....

I guess it's the WAY the magnetic lines are propagating.... with an ANTENNA, you have ELECTRICAL waves and MAGNETIC waves at 90 degrees to each other propagating AWAY from the antenna. With an MRI you have <I guess> a COIL (kind of like an electromagnet) which goes over <around> the person's body. I remember as a kid taking a 10 penny nail, a wire, and a battery and making an electro-magnet.... MRI is simiilar.

I've heard stories of ppl getting killed by FIRE EXTINGUISHERS in MRI machines, when the extremely strong electromagnetic field actually pulled the fire extinguisher off the wall and smashed it into the patient killing them. Now-a-days they have MRI SAFE extinguishers.

Another example of a strong magnetic field was when I used to work as a consultant to a Medical College in NYC and had inadvertantly passed through a lab which had either an MRI-type machine, or else a particle accelerator in operation as I was tracing out piping and wiring in the walls, floors and ceilings surrounding the lab areas. On my way home, when I stopped for gas, NONE of my credit cards worked anymore. Turns out the strong magnetic field(s) had wiped out virtually ALL my credit cards in my wallet!

Lastly, where I live now, I'm about (roughly) 6 blocks from my local hospital. Rather than have a PERMANENT MRI wing in the hospital, they rent an MRI van, which pulls up to the building for weeks/months at time. When the MRI is operating, even though I am 6 blocks away, I can detect it's field on HF, VHF, & UHF 6 blocks away on the following bands: 30M, 20M, 17M, 15M, 12M, 10M, 6M, 2M, & 70CM. It doesn't seem to give me any RFI on 40 or 80M, I don't have a decent antenna for 160M so I dunno if it would affect me or not. BC band is no problem, so I guess 160 would be okay.

Two more interesting experiments: When in the presence of a strong RF field, one can actually generate electrical power from it, as many ppl do who are close to a high powered AM broadcast band transmitter (530 - 1600 KHz).

Another interesting (but SCARY) thing I've seen is BC band interference from nuclear power stations. The two WORST were: Peach Bottom in York, PA, and the nuclear power plant in Zion, IL (not sure if either of them are still in service.) Neither of them ever affected my HF/VHF mobile operations, but they sure did wipe out AM broadcast band on the car stereo when approaching the sites years ago! Not related to the 50KW bracelet heating phenomenon, but interesting (freaky) nonetheless!

 

[linearone]

He said he was wearing a gold bracelet , you do have a point about it acting as an antenna, but I think 50k is a bit far fetched, where would you get a linear to push that much wattage or even an antenna that could handle it?


T23

Boy, you are new here. I know three trucks that do 50kw. all within 100 miles of me. I know of about half a dozen 25kw trucks in about the same radius and over 18 that are 10kw capable. There are probably more that I dont know about.

Welcome to American CB radio.

 

[linearone]

The story is interesting. Back 15 years ago there were guys who ran in the 50 KW range at the New Jersey keydowns. I remember the big Bird line sections and the meters were showing the claimed power. I was not completely convinced someone didn't tamper with the slugs until I saw one of the biggest corona arcs in my life. This guy keyed his mic and a corona arc ignited where the hardline connected to the base. It almost burned a hole through the sheet metal roof in about 3 seconds.

Yup that was Double Nickel from CT. It burned through the Heliax because it was too close to the roof I believe.

 

[W5LZ]

An MRI 'pulls' in metal objects from 10 feet away? Someone killed by a fire extinguisher 'pulled' off of a wall by an MRI machine? Can you document those occurrences? Otherwise, I really don't think I'd even come close to believing that one! Sorry.
- 'Doc

 

[Shockwave]

I never knew this effect was so powerful either until recently. It turns out they really are that strong. There is a show on TV called "1000 Ways to Die" and they document real deaths with locations and dates that have occurred in unusual ways. In one case a man pulled a gun on a nurse in the MRI room. Apparently she knew how strong this field is and somehow activated the MRI unit. Not only did it rip the gun out of his hand from nearly 10 feet away, what the nurse didn't know what this person had some type of metallic plate in his head. His head was pulled into the machine with such force it killed him.

 

[T23]

Those who are doing 50kw 10kw and so on and so forth are bleeding over many channels....:mellow:

Theres a local around here broadcasting on channel 1 and you can hear his "music" on the next 6 channels ( and if you have the lower frequencies , you could hear him there too )

Not saying these types of wattages aren't possible by how convenient is it really?

T23

 

[mackmobile43]

Those who are doing 50kw 10kw and so on and so forth are bleeding over many channels....:mellow:

Theres a local around here broadcasting on channel 1 and you can hear his "music" on the next 6 channels ( and if you have the lower frequencies , you could hear him there too )

Not saying these types of wattages aren't possible by how convenient is it really?

T23

If you can get a 3 phase hookup without anyone getting nosy then sky's the limit.